• K. Gianikellis
  • J. Dura


INTRODUCTION It is well known that physically handicapped persons can participate in many sport modalities. However, the disability of blind people is not compatible with shooting drills or archery. Our endeavor in this study is to establish the theoretical frame for the development of system that is able to generate in real time acoustical signals (feedback information) making possible the practice of shooting sports by persons with this kind of disability. To this purpose we use sonic digitizing to convert information respect to three-dimensional coordinates of ultrasound emitters to digital values, based on the properties of sound propagation. The measurement chain consists in a SAC Sonic Digitizer (GP8-3D) that communicates with a personal computer via a parallel interface (PI012), for higher data rate throughput, and a synchronized microphone sensor to detect the instant of triggering. The sampling rate of the sonic digitizer is 66.6 Hz divided by the number (k=3) of sound emitters to be used and its precision is P=0.115mm for a range of measurement D=2625mm (1 :22744). Three ultrasound emitters are fixed on the rifle and one of them is selected as origin, where an orthogonal local system of reference (SI) is established. In this way the kinematics of the moving rifle with respect to the absolute system of reference (Sg) is fully defined if the position of the three emitters is continuously monitored. Also the direction of the aiming line respect to the local system of reference can be monitored (rifle calibration). This implies that it is possible to determine the rifle kinematics (aiming line) respect to the center of the target by means of matrix transformations procedures and calculate the distance of the aiming line respect to the previously calibrated center of the target Knowing the distance of the aiming point (intersection of the aiming line with the plane of the target) to the center of the target, personal computer produces a sound of variable intensity and frequency as a function of that distance to inform subJect via earphones about the proximity to the target. CONCLUSION In this study a feedback loop takes place respect to the position and orientation of the rifle to the target that guides blind persans to adjust continuously the position of the rifle. REFERENCES Gianikellis, K. et al., (1991). A Sonic Digitizing technique for Biomechanical Analysis and Training in movements and Sports of high Precision based on Real time 2nd Biofeedback (Abstract). In IOC World Congress on Sport Sciences, Barcelona. Spain Engin, AE. et al., (1984). Kinematic and force data collection in Biomechanics by means of Sonic Emitters. -I: The Kinematic Data Collection Methodology-. Journal of Biomechanical Engineering, v. 106, 203-211
Equipment / Instrumentation